1. Technical Field
The following description relates to one or more developer supply devices configured to supply charged powdered development agent to an intended device.
2. Related Art
A developer supply device has been known that includes a developer holding member (a development roller), an upstream developer transfer unit, and a downstream developer transfer unit.
The developer holding member is disposed to face an electrostatic latent image holding body (a photoconductive drum) in a predetermined development area. The developer holding member has a developer holding surface on which charged development agent is held and carried.
The upstream developer transfer unit has an upstream transfer surface, which is disposed upstream relative to the development area in a moving direction of the developer holding surface (i.e., in a rotational direction of the development roller) so as to face the developer holding surface across a predetermined distance. The upstream developer transfer unit is configured to generate an upstream transfer electric field (i.e., an electric field for transferring the development agent held on the upstream transfer surface from an upstream side to a downstream side in the moving direction of the developer holding member).
The downstream developer transfer unit has a downstream transfer surface, which is disposed downstream relative to the development area in the moving direction of the developer holding surface so as to face the developer holding surface across a predetermined distance. The upstream developer transfer unit is configured to generate a downstream transfer electric field (i.e., an electric field for transferring the development agent held on the downstream transfer surface from an upstream side to a downstream side in the moving direction of the developer holding member).
In the above configuration, the electric fields, for transferring the charged development agent from an upstream side to a downstream side in the moving direction of the developer holding member, are generated in spaces on the upstream transfer surface and the downstream transfer surface. Thereby, the development agent is transferred, on each of the upstream transfer surface and the downstream transfer surface, from the upstream side to the downstream side in the moving direction of the developer holding member.
The development agent, conveyed by the upstream developer transfer unit, is transferred onto the developer holding surface in a position where the upstream transfer surface faces the developer holding surface (i.e., a circumferential surface of the development roller). Thereby, the development agent adheres to the developer holding surface. Namely, the development agent is held and carried on the developer holding surface.
A part of the development agent held on the developer holding surface is supplied and consumed in the development area to develop an electrostatic latent image. In other words, when reaching the development area, the development agent held on the developer holding surface partially adheres to positions, corresponding to the electrostatic latent image, on an electrostatic latent image holding surface that is a circumferential surface of the electrostatic latent image holding body.
The remaining part, of the development agent held on the developer holding surface, which has not adhered to the electrostatic latent image holding surface (i.e., which has not been consumed in the development area), is retrieved by the downstream developer transfer unit, and then transferred, on the downstream transfer surface, from the upstream side to the downstream side in the moving direction of the developer holding surface.